Doublet gem construction



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DOUBLET GEM CONSTRUCTION Filed April 12, 1968 DIAMOND I8 INTERFACIALLY SEIZED F IT RUTILE ZIRCON STRONTIUM TITANATE INVENTOR Uoited States Patent ABSTRACT THE DISCLOSURE Doublet gemstone having a crown or upper portion of relatively high hardness and predetermined optical dispersion having its undersurface disposed in interfacially seized engagement with a complementally configured upper surface of alower or pavilion portion of lesser hardness and higher optical dispersion.

This invention relates to doublet gemstones and particularly to an improved construction for doublet gemstones'and is a continuation-in-part of my application Ser. No. 441,477, filed Mar. 22, 1965.

In its broad aspects the subject invention provides for an improved doublet construction in .which a crown portion of high hardness and predetermined optical dispersion is disposed in effectively perinanent interfacially seized engagement with a lower or;pavilion portion of lesser hardness and higher optical dispersion.

This invention makes possible, therefore, the utilimtion of a hard material to form the outside facets exposed to wear by the user while color and sparkle are produced by a highly dispersive material having a lower hardness whichforms the bottom or protected portion of the jewel. Such new combinations are then adapted to provide highlyfdesired visual effects often referred to as color, beauty, life, fire, sparkle or brilliance" together with a durability on the exposed outer portion that is equal to or close to that of diamond. While efforts to achieve these highly desired and advantageous properties have been sought in the past through the use of transparent cements of proper color and refractive properties at the doublet interface, the general susceptibility of such cements to solvent attack and the like have resulted in a sufficient impermanence of connection as to effectively preclude the widespread use of such doublet gemstone constructions.

The object of this invention is the provision of an improved construction for doublet gemstones in which the uppej and lower portions thereof are effectively permanently secured together in optically seized interfacial relatifbn.

A-"diagrammatic sectional view of my invention is shown in FIG. 1, and as there shown the new and improved gemstone construction consists of a top or crown portion 1 which is disposed in "effectively permanent secured relation, as by a permanently seized wringing fit, to a lower or pavilion portion 2. As will be disclosed in more detail hereinafter the interface or mating surfaces 3 of parts 1 and 2 are polished and lapped to such a high degree as to be wrung together to the point of optical seizure, otherwise a highly undesirable result, to effect a permanent interconnection thercbetween.

The top portion 1 of the new jewel construction is desirably constituted of any extremely hard material such as diamond (carbon), sapphire (A1 0 spinel (MgO.Al O topaz ([AlF] SiO or quartz (SiO which may or may not possess high optical dispersion. The bottom portion 2 of the jewel is desirably constituted of any material having a relatively high optical dispersion I 3,528,261 Patented Sept. 15, 1970 ice such as zircon (SrSiO rutile (TiO or strontium titanate (-SrTiO which may and usually will not have a hardness as great as the top portion 1.

The upper and lower portions will include complementally configured mating surfaces and are desirably faceted on the exposed surfaces. thereof to enhance their jewel like appearance. Q I

The use of a hard material for the top portion 1 serves a desirable protective function. The refraction and dispersion ffects within the combination may be understood from the following explanation:

Again ieferring to the drawing, a ray of white light 4 which impinges normal to interface surfaces 3 and 5 will be internally reflected at points 6 and 7 without dispersion. At point 8, however, refraction will occur due to the difference between the refractive indices of the materials from which parts 1 and 2 are constructed. Since the material from which part 2 is constructed will have a relatively high optical dispersion the spread between red ray 4!? and blue ray 4b will be substantial. These rays will then be further refracted at points 9r and 9b. However, the increase in the spread or dispersion ofdifferent colors contributed by the interface formed by surface 10 between part 1 and the surrounding air will usually be less than'jthat due to interface 3. Due to the optical dispersion effects previously described an observer whose eye is at point 11 will see only a relatively narrow band of colors" or only one color rather than white light. If the direction of light ray 4 is reversed an observer whose eye is at a point 12 will also see a narrow band of colors or only one color, rather than white light.

A further color-selective effect will also occur when angle 13"between ray 4 and a normal line 13a perpendicular to surface 17 at point 6 is smaller than the critical angle for the material from which part 2 is constructed. For exaniple, when part 2 is constructed from strontium titanate, the critical angle for strontium titanate relative to air is approximately 24.5 Therefore, when angle 13 is slightly smaller than 245 the red rays will pass through to the surrounding air and will, for practical purposes, be lost, as indicated by dotted ray lines 14. However, since the critical angle will be somewhat less for blue rays, internal reflection of blue rays will occur and an observer whose eye is at point 11 will see bluish colors but no red colors. Angle 13 will approach the critical angle when the angle 15 between ray 4 and surface 5 is reduced from 90 to a sufficiently small value. This critical angle effect and the accompanying color effects will, of course, be enhanced if the bottom part 2 is constructed of a material having a relatively high optical dispersion.

The angles between facet surfaces 5, 10, 16, 17 and 18 shown in FIG. 1 may be varied without departing from the basic principles described above. As will be apparent to those skilled in this art, there may be numerous facets similar to those surfaces indicated at 5, 10, 16, 17 and 18 around the jewel in accordance with usual gem-cutting practice and interface surfaces 3 may also be located above or below the level shown. A relatively flat bevel, such as indicated by 19, may be added if desired.

Varying degrees of attractive visual effects may be obtained and various combinations of attractive visual effects may be obtained by variation in the angles between facets and by using different combinations of hard and highly dispersive materials.

As pointed out above the doublet halves are secured in permanent interfacially elongated relation by means of a seized fit at the interfaces thereof. The obtaining of able, for example, through a degree of flatness illustrated by the presence of only such a relatively smalLportion of an interference fringe such that no color variation can be seen when an optical test fiat is laid upon the jewel surface.

One suitable method of obtaining and ascertaining a desired degree of flatness to obtain a permanent seized fit is to first work the mating surface against the flat glass or metal lapping surfaces of substantially larger area to produce a very finely ground fiat surface thereon. This is followed by progressively finer lapping surfaces with very fine grinding powders to obtain highly polished surfaces in the orders of flatness within a few hundred angstrom units or the like.

When so prepared the desired degree of flatness may be ascertained by mounting the doublet portion on a test flat and observing the desired degree of absence of color variation or color fringes therebetween under suitable illumination and with an optical magnifier in the order of x power.

Once the desired degree of flatness for the mating surfaces has been obtained, the desired seized fit is obtained by manipulating the doublet halves past the stage of the conventional wringing fit to a stage where the frictional forces are in the order of ten thousand times the weight of the doublet halves. Such operation can be performed either manually or by suitable apparatus, preferably in conjunction with a suitable force gauge to indicate the progressive increase in the degree of magnitude of the frictional forces and the probable limit thereof that can be reached before damage to the interface is effected.

A suitable machine system would operate to slide the mating parts of the doublet together under graduallyincreasing force perpendicular to the interface. By means of a force gauge responsive to the force required to slide the mating parts relative to each other, the machine could be stopped when a predetermined functional force has been built up. Then the final alignment of parts could be achieved by hand or a power-driven fixture.

Having thus described my invention, I claim:

1. A doublet gemstone construction comprising an externally multifaceted upper portion of relatively high hardness and predetermined opticaldispersion A having its undersurface lapped to a degree of fiatness characterized of a substantially total absence of interference color fringes when disposed adjacent an optical test flat,

a complementally peripherally contoured lower portion of lesser hardness and higher optical dispersion than said upper portion having its upper surface lapped to a degree of flatness characterized by a" substantially total absence of interference color fringes when disposed adjacent an optical test fiat, said undersurface of said upper portion being disposed in effectively inseparable interfacially seized fit engagement with the said upper surface of said lower portion, said engagement characterized by lateral interfacial frictional forces of a magnitude about 10,000 times the weight of said upper and lower portions. 2. The doublet gemstone as set forth in claim 1 wherein said upper portion thereof comprises diamond.

3. The doublet gemstone as set forth in claim 1 wherein said upper portion thereof comprises sapphire.

4. The doublet gemstone as set forth in claim 1 wherein said upper portion thereof comprises spinel.

5. The doublet gemstone as set forth in claim 1 wherein said upper portion thereof comprises topaz.

6. The doublet gemstone as set forth in claim 1 wherein said upper portion thereof comprises quartz.

7. The doublet gemstone as set forth in claim 1 wherein said lower portion thereof comprises zircon.

8. The doublet gemstone as set forth in claim 1 wherein said lower portion thereof comprises rutile.

9. The doublet gemstone as set forth in claim 1 wherein said lower portion thereof comprises strontium titanate.

References Cited OTHER REFERENCES Kraus et al.: Gems and Gem Materials, by E. H. Kraus and C. B. Slawson, McGraw-Hill, New York, 1947, pp. 171-173 relied on.

Smith: Gemstones, by G. F. H. Smith, Methuen &

Co., Ltd., London, England, as revised by T. C. Phillips,

1958, pp. 206-207 relied on.

F. BARRY SHAY, Primary Examiner US. Cl. X.R. 

